How to add a custom initializer to a struct without losing its memberwise initializer

All structs in Swift come with a default memberwise initializer, which is an initializer that accepts values for all the properties in the struct. However, as soon as you add your own initializer to the struct that memberwise initializer goes away, because it’s possible you’re doing special work that the default initializer isn’t aware of.

If you want to keep both the default initializer and your own custom ones, there’s a simple trick: create your initializers inside an extension rather than as part of the main struct definition.